Re: [Qemu-devel] TCP_NODELAY for -redir

[Daniel Jacobowitz]

On Mon, Nov 13, 2006 at 02:30:27PM -0500, Daniel Jacobowitz wrote:
> I was trying to run GDB remote debug tests through a -redir socket
> today.  It crawled unbelievably.  Paul guessed that slirp wasn't using
> TCP_NODELAY, and Nagle was to blame.
> 
> He was even righter than usual.  Adding TCP_NODELAY speeds up this
> particular workload by (very approximately) 54x.  See trivial attached
> patch.
> 
> Is this going to bite other things, i.e. does it need to be
> configurable?

No comments on this...

My reasoning, by the way, was that slirp is being used as a TCP-to-TCP
gateway.  I think that if we were to use nagle here, we'd end up doing
it twice: once at the sender inside the guest, and once again on the
host's TCP stack.  Using TCP_NODELAY lets the guest take
responsibility.


-- 
Daniel Jacobowitz
CodeSourcery